Electron tube



May 31, 1966 w. R. STUART ELECTRON TUBE Filed July 22, 1963 INVENTOR. 7WILLIAM R. STUART ATTORNEY 3,254,258 I ELECTRON TUBE William R. Stuart,San Carlos, Calif., assignor to Eitel- McCullough, Inc., San Carlos,Calif., a corporation of California Filed July 22, 1963, Ser. No.296,575 4 Claims. (Cl. 313-256) This invention relates to electron tubesand more particularly to an electron tube having an improved electrodealignment arrangement.

Recent requirements have made it necessary for electron tubes to be ableto meet new specifications calling for ability to withstand extremeshock and vibration and also requiring improved accuracy in electrodealignment. In the past, a dielectric electrode support pin was oftenused to hold the electrodes of an electron tube in alignment. However,thehot cathode in such an electron tube expands and contracts out ofproportion with respect to the other electrodes which are supported bythe dielectric electrode support pin. Consequently, the priorarrangement of providing alignment between the various electrodes of atetrode tube, for example, was to braze the control and screen gridstructures to metallized bands on the dielectric electrode support pin.The cathode structure could not be brazed to the dielectric electrodesupport pin because of its disproportionate movement with respect to thecontroland screen grid structure which would, cause the portion of thecathode structure'adjacent the area of the braze to severely warp, andthis would finally result in the destruction of the tube. Hence, theprocedure previous to this invention was to provide an extremely finetolerance on the' surface of the dielectric electrode support pin whichextended through a precisely formed aperture in the cathode structure topermit the cathode structure to slide along the dielectric electrodesupport member in accordance with its expansion and contractioncharacteristics. Providing a fine tolerance on the external surface ofthe dielectric electrode support pin was expensive and time consuming,but was necessary in prior electron tubes. However, in spite of thegreat care that was taken in providing the fine tolerance on thedielectric electrode support pin, a large proportion of the number ofelectron tubes previously made had to be discarded when it wasdiscovered that the space between the aperture in the cathode structureand the surface of the dielectric electrode support. pin was too largecausing unwanted noise. in shock and vibration tests. A need existed foran electron tube having an improved electrode support arrangement toconsistently 3,254,253 Patented May 31, 1966 "ice ' URE 1, and

FIGURE 3 is an enlarged elevational view partly in section of thecathode and the dielectric electrode sup portpin at operatingtemperature.

Referring in more detail to the drawing, an attempt will be made todescribe first the construction which is either shown in the Drieschmanet al. Patent No. 2,472,- 942 or utilized in improved versions thereofprior to this invention. The tube of FIGURE 1 comprises a heater coil 1,a cathode 2, a control grid 3, a screen grid 4 and an anode 5.

The envelope for the tube is formed in part by the inverted cup-shapedmetal anode 5. The remainder of the envelope is formed by the metal ring7, brazed to the bottom of theanode and to the top of a ceramic cylinder8 which is metallized in conventional manner for this purpose; a metalsealing ring 9 and a metal shell 10 which are sealed together by a finalbraze or weld 11, with ring 9 being brazed to the bottom of ceramiccylinder 8 which is metallized for this purpose; and a ceramic headerdisk 12 which has an annular metallized area brazed to shell 10.

As regards terminals for the electrodes, the outer portion of the anodeof course serves as its own terminal. The ring 9 and shell 10 can serveas the terminal for the screen grid 4. The remaining terminals areformed by pins sealed in the header disk 12. Eight small diameter pins(only four of which are shown in FIGURE 1) are arranged in a circulararray around a large diameter center pin 22. Although eight small pinsare employed, only six of them are required as terminal-s. In theconstruction shown, four pins including pins 14 and 18 serve as cathodeterminals and pin 17 serves as heater terminal. Pin 15 is shown inFIGURE 1 as one of the pins not required as a terminal. The center pin22 is the control grid terminal. The center pin is sealed in the headerby metallizing the wall of the aperture in the header and brazing .thepin thereto. In the case of .the small pins the apertures in the headerare not metallized but instead an annular area is metallized on thebottom of the header around each pin. A copper Washer 24 is brazed tothe meet the high standards required under shock and vibratube having anenvelope enclosing cylindrical electrodes including a cathode. Adielectric electrode support pin having a tapered end portion isprovided to support the tube electrodes. One of the electrodes otherthan the cathode is connected to the dielectric electrode support pin.An annular flexible metal member which has an aperture therein isconnected to the cathode. The tapered end portion of the dielectricelectrode support pin extends through the aperture and engages theannular flexible metal member to maintain alignment of the cylindricalcathode during operation of the tube.

These and other objects and features of advantage will become apparentfrom a reading of the following detailed description wherein referenceis made to the accompanying drawing in which:

metallizing and the pin, and a kovar washer 25 is brazed to the copperwasher and to the pin.

The anode structure is completed by brazing on conventional metalcooling fins 27 and a two-piece metal cover 28 over the pinched-01fexhaust tubulation 29. The

small wires 34 which pass through apertures in the disk and are spotwelded at each end to the posts. A conventional getter strip 35 is spotwelded to post 32. The grids 3 and 4 are conventional cage-type wirestructures, each having an inverted cup-shaped configuration. It will benoted that the screen and control grids and the cathode all have metalend portions 36, 37 and 38, respectively.

Control grid 3 is supported by means of a metal ring 40 attached to thebottom thereof and having two, down.-

wardly extending projections 41 on its diametrically opposite sides(only one such projection being visible in FIGURE 1). A supporting yokestructure is formed by two U-shaped rods 42 brazed at their ends to theprojections 41 and at their center in a slot in the top of the centerpin 22. Cathode support ring 44 has four channelshaped legs 45. Thechannel construction extends along the sides of the pins 14 and 18. Thisconstruction is important in order to braze the legs 45 to the pins andmakes a much more rigid structure. Continuing with the description ofthe cathode support members, a very thin metal heat dam 46 is attachedto the lower end of the cathode can. The lower end of the heat dam isspot welded to the outer surface of the support ring 44.

The heater posts 31 and 32 are brazed at their lower ends in legs 47 and48. As in the case of the cathode support legs, and for the samereasons, the heater legs are channel-shaped including the portion whichextends over and is brazed to the terminal pin 17. A ceramic rigidifyingdisk 50 is metallized on its outer periphery and brazed to the cathodesupport ring 44. The disk 50 is apertured to receive heater posts 31 and32, and the walls of apertures are metallized and brazed to the posts.

The lower end of the screen grid 4 is attached to a metal cone 52mounted on a metal support ring 53. The cone is attached to ring 53 byscrews 54 (preferably three) which abut the cone and are received inthreaded apertures in the ring. Ring 53 has a three-part shapecomprising a cylindrical side portion 55 brazed to shell 10, a flatcone-supporting portion 56, and a downturned centering flange portion 57at its inner periphery. The apertures for screws 54- are so positionedthat when the screws are inserted in members 52 and 53, member 52 iscentered with respect to flange 57.

Referring to all the figures, a dielectric electrode support pin 60 isshown. Pin 60 is made of ceramic and its periphery is metallized whereit passes through the screen and control grid ends 36 and 37 and isbrazed to these ends. In addition, the pin has a large disk portion 61between the cathode and control grid to reduce the capacitance betweenthese electrodes.

The pin 60 has a tapered end portion 63. The metal end portion 38 of thecathode 2 is a thin annular flexible metal member consisting ofHastelloy B metal, which is the trade name of a nickel based alloycontaining small amounts of molybdenum, iron and carbon. Hastelloy B hasan expansion characteristic similar to the nickel cathode 2 and stillretains its hardness at tube operating and processing temperatures. Themetal end portion 38 is preferably 2 mils thick and is spot weldedaround its outer edge to the cathode 2.

The tapered end portion 63 of the dielectric electrode support pin 60extends through an aperture in the metal end portion 38. The dielectricelectrode support pin 60 has one portion which has a diameter that islarger than the diameter of the aperture in the metal end portion 38 andanother portion which has a diameter smaller than the diameter of theaperture in the metal end portion 38. Thus, in operation, as can be seenfrom FIGURE 3, the cathode 2 expands when hot and moves closer to thedisk portion 61 of pin 60. The metal end portion 38 flexes to permit thecylindrical cathode 2 to be kept in concentric alignment with respect tothe cylindrical control grid 3. This arrangement eliminates noise whenthe tube is subjected to shock and vibration applications.

The teaching of this invention may be practiced by utilizing any meansat the end portion of the dielectric pin 60 having a surface extendingat an angle to the axis of the pin functioning similarly to the taperedportion 63 so as to engage the member 38 of the cathode 2 in order tomaintain alignment of the cathode cylinder when the tube is inoperation.

It is to be understood that the above-described arrangements are simplyillustrative of the application of the principles of the invention.Numerous other arrangements may be readily devised by those skilled inthe art which will embody the principles of the invention and fallwvithin the spirit and scope thereof.

I claim: 1. An electron tube having an envelope enclosing cylindricalelectrodes including a cathode, a dielectric electrodesupport pinmounted between said electrodes, said dielectric electrode support pinhaving a tapered end portion, at least one of said cylindricalelectrodes other than said cathode being connected to said dielectricelectrode support pin, and an annular flexible metal member connected tosaid cylindrical cathode, said annular flexible metal member having anaperture therein, said tapered end portion of said dielectric electrodesupport pin extends through said aperture and the tapered'surface ofsaid end portion engages said annular flexible metal member to maintainalignment of the cathode during operation of the tube, the taperedportion of said pin having a maximum diameter which is larger than saidaperture, and the maximum diameter end of said tapered portion islocated along said pin on the side of said flexible member toward saidconnection between the pin and said at least one other electrode.

2. An electron tube having an envelope enclosing cylindrical electrodesincluding a cathode, a dielectric electrode support pin mounted betweensaid electrodes, said dielectric electrode support pin comprising anelongated ceramic member having a tapered end portion and at least onemetallized surface portion, at least one of said cylindrical electrodesother than said cathode being connected to the metallized surfaceportion of said dielectric electrode support pin, and a thin annularflexible metal member connected to said cylindrical cathode, said thinannular flexible member having an aperture therein, said tapered endportion of said dielectric electrode support pin extends through saidaperture and the tapered surface of said end portion engages said thinannular flexible member to maintain alignment of the cathode duringoperation of the tube, the tapered portion of said pin having a maximumdiameter which is larger than said aperture, and the maximum diameterend of said tapered portion is located along said pin on the side ofsaid flexible member toward said connection between the pin and said atleast one other electrode.

3. An electron tube having an envelope enclosing cylindrical electrodesincluding a cathode, a dielectric electrode support pin mounted betweensaid electrodes, said dielectric electrode support pin comprising anelongated ceramic member having a tapered end portion and at least onemetallized surface portion, at least one of said cylindrical electrodesother said cathode being connected to the metallized surface portion ofsaid dielectric electrode support pin, and a thin annular flexible metalmember connected to one end of said cylindrical cathode, said thinannular flexible member having an aperture therein, said tapered endportion of said dielectric electrode support pin extends through saidaperture and engages said thin annular flexible member, said thinannular flexible metal member having an aperture therein, said taperedend portion of said dielectric electrode support pin having one portionhaving a diameter larger than the diameter of said aperture and anotherportion having a diameter smaller than the diameter of said aperture,said thin annular flexible metal member consists of Hastelloy B metal.

4. An electron tube having an envelope enclosing cylindrical electrodesincluding a cathode, a dielectric electrode support pin mounted betweensaid electrodes, said dielectric support pin comprising an elongatedceramic member having a tapered end portion and a pair of metallizedsurface portions, a cylindrical control grid connected to one of saidpair of metallized portions, a cylindrical screen grid connected to theother of said pair of metallized portions, and a thin annular flexiblemetal member connected to said cylindrical cathode and in engagementwith said tapered end portion of said dielectric electrode support pin,said thin annular flexible metal member having an aperture therein, saidtapered end portion of said dielectric electrode support pin having one5 7 portion having a diameter larger than the diameter of said apertureand another portion having a diameter smaller than the diameter of saidaperture, said thin annular flexible metal member consists of HastelloyB metal.

References Cited by the Examiner UNITED STATES PATENTS 6 2,939,9886/1960 Culbertson et a1 313-250 3,132,274 5/ 1964 Kendall 313363 JAMESD. KALLAM, Acting Primary, Examiner.

JOHN W. HUCKERT, Examiner.

A. J. JAMES, Assistant Examiner.

1. AN ELECTRON TUBE HAVING AN ENVELOPE ENCLOSING CYLINDRICAL ELECTRODESINCLUDING A CATHODE, A DIELECTRIC ELECTRODE SUPPORT PIN MOUNTED BETWEENSAID ELECTRODES, SAID DIELECTRIC ELECTRODE SUPPORTED PIN HAVING ATAPERED END PORTION, AT LEAST ONE OF SAID CYLINDRICAL ELECTRODES OTHERTHAN SAID CATHODE BEING CONNECTED TO SAID DIELECTRIC ELECTRODE SUPPORTPIN, AND AN ANNULAR FLEXIBLE METAL MEMBER CONNECTED TO SAID CYLINDRICALCATHODE, SAID ANNULAR FLEXIBLE METAL MEMBER HAVING AN APERTURE THEREIN,SAID TAPERED END PORTION OF SAID DIELECTRIC ELECTRODE SUPPORT PINEXTENDS THROUGH SAID APERTURE AND THE TAPERED SURFACE OF SAID ENDPORTION ENGAGES SAID ANNULAR FLEXIBLE METAL MEMBER TO MAINTAIN ALIGNMENTOF THE CATHODE DURING OPERATION OF THE TUBE, THE TAPERED PORTION OF SAIDPIN HAVING A MAXIMUM DIAMATER WHICH IS LARGER THAN SAID APERTURE, ANDTHE MAXIMUM DIAMETER END OF SAID TAPERED PORTION IS LOCATED ALONG SAIDPIN ON THE SIDE OF SAID FLEXIBLE MEMBER TOWARD SAID CONNECTION BETWEENTHE PIN AND SAID AT LEAST ONE OTHER ELECTRODE.